1. Field of the Invention
The present invention is broadly concerned with an improved process for the recovery of dilute printing ink wastes, and particularly those of a single primary color, generated as a byproduct of commercial printing operations. More particularly, the invention si concerned with such a process wherein dilute washup fluids containing water, a minor amount of residual ink, and typical ink carriers, is initially acidified to create a pin floc, whereupon the acidified fluid is reacted and converted by contacting the fluid with a stream of steam. The invention thus permits the recovery and reuse of valuable single color ink wastes, and the production of reconstituted inks therefrom.
2. Description of the Prior Art
U.S. Pat. No. 5,200,094 describes a process wherein ink wastes (e.g., a chemically treated and concentrated mixture of ink wastes derived from a number of printing runs) are treated in a confined zone with steam in order to convert the residual ink into a product which can be readily reconstituted as high quality black ink. The process described in the '094 patent represents a significant break through in the art, inasmuch as it provides a practical, low cost way to treat and reuse the considerable volumes of ink wastes generated in commercial printing plant operations. Such wastes have presented a significant disposal problem in the past, owing to increasingly stringent environmental regulations prohibiting direct disposal of the ink wastes.
In addition, a related patent application (Ser. No. 08/033,868 filed Mar. 19, 1993) describes a similar ink waste conversion process wherein use is made of dilute washup fluids containing water and a minor amount of residual ink. Here again, this process contemplates contacting the dilute washup material with a stream of steam in a confined zone. The process of this patent application thereby eliminates the need for preliminary chemical treatment and concentration of the recovered printing ink wastes.
While the processes described in this patent and pending application have proved to be highly successful, in general they have been most successfully implemented with mixtures of different color ink wastes and the resultant production of reconstituted black inks. Attempts at using the processes for the production of single color reconstituted inks have been less successful, resulting in viscous filter pressed material which tend to rapidly plug the press and are difficult to reformulate with ink carriers. Black printing ink is relatively low in cost and readily available from other sources. However, some single color inks (e.g., red, blue, purple, etc.) are considerably more expensive. Accordingly, if these processes could be improved to more readily produce acceptable reconstituted single color inks, the economic benefits would be significant. U.S. Pat. No. 5,200,094 and the aforementioned pending patent application are incorporated by reference herein.